Probabilistic model for predicting instantaneous structural deterioration due to earthquakes

Due to the relatively short duration of earthquakes, most studies simplify their impact on structures by considering the total effect of each event rather than modelling the instantaneous accumulation of damage during the event itself. This approach may underestimate performance degradation, as incremental damage occurring during the shock can lead to an immediate reduction in capacity. Furthermore, most structures experience multiple earthquakes throughout their service life, and aftershocks can significantly compromise structures already weakened by prior seismic events. A framework that directly incorporates time history effects into system performance predictions would enable a more accurate assessment of structural response to future seismic events and would synergize with available methods to generate realistic mainshock-aftershock sequences. This work uses recently proposed formulations based on Stochastic Differential Equations (SDEs) to analyse the instantaneous damage accumulation within sequences of earthquakes. Models are calibrated based on Finite Element Analyses, resulting in physics-based, probabilistic surrogate models, which can reproduce similar results and associated uncertainties) in a fraction of the time. Finally, the proposed method is integrated within a reliability-based formulation to obtain time-varying fragility curves for an example structure before a shock, during a shock, and after a realistic aftershock sequence.